A typical railroad car has an elongated frame; and a wheeled truck assembly is at each end of the car, connected to the frame to rotate about a substantially vertical axis. Each wheeled truck assembly has flanged wheels, that are adapted to roll on a pair of track rails. With the wheels on the rails, there may be clearance of perhaps only approximately 10 inches between the tops of the rails and the underside of the railroad car frame.
Routine maintenance may require that the car frame be elevated somewhat to increase this clearance. One specific form of maintenance may require that the railroad car be completely removed from one wheeled truck assembly, to allow such truck assembly to be replaced with another. To do this, the one end of the car may be lifted vertically perhaps 10-25 inches, while the other end of the car remains supported on the other wheeled truck assembly. With the one car end so elevated, both the old and the new truck assemblies can be rolled on the rails, respectively from and to being under the car. Other forms of maintenance may require someone to crawl about under the car, where this increased clearance would also be benefical.
One way of lifting one end of the railroad car is by means of a crane, by connecting its lift line to the car frame, such as at the car coupling. This of course requires the presence of a high capacity crane, that can carry the load of the car; which crane typically will be quite large and represent a significant capital investment. Moreover, such a crane may be mounted on a special railroad service car or road vehicle, so that it is not portable. Also, if limited to roll along on track rails, the crane may not be very convenient to move from one site need to another; or if on a road vehicle and/or because of its size, the crane may be used at only certain rail sites.
Another way the railroad car can be removed from the wheeled truck assembly is by means of a pair of separate lift jacks, interposed between the underlying rail bed and each side of the car frame. These jacks are relatively inexpensive, and quite portable. However, as the separate jacks bear against the rail bed, special shoring effort may be needed, by placing planks or the like under the lift jacks, to provide added stability to the jacks and/or to prevent the jacks from sinking into the rail bed. Moreover, with the jacks on opposite sides of the car, several people may be needed to jack the railroad car up and down. The overall time and/or cost and/or convenience, from a labor standpoint, to operate such lift jacks, thus may not be too appealing.
Moreover, risks frequently linger on with the use of either the crane or paired lift jacks, as without other bracing or support means, they remain the only support of the railroad car during the time the wheeled truck may be removed from the car, and/or while someone is under the car for servicing. A cross wind may cause the crane-suspended car to sway, and the paired jack-supported car to topple sideways off the jacks to drop onto the rails or rail bed; which can be both dangerous to personnel and destructive to property. Failure of the crane and/or lift line, or of either jack, can also drop the raised car to the rails or rail bed.
The present invention is directed to improved portable jack assembly means that overcome one or more of the drawbacks set forth above.